Why does the mobile phone automatically send text messages? It's not a preset text message, but the text message reads: I'm using your mobile phone. Send to another number.

If I'm not mistaken, it should be that you installed another card before your mobile phone, then set the number of someone you know who locked the card and set an alarm device in a similar anti-theft device, that is, your mother's number, so that when you change the card, your mobile phone will automatically recognize your mobile phone, and then send this short message to your preset number.